Fabricated blade and bucket rotor assembly



Feb. 14, 1961 R. E. WARREN EIAL 7 4 FABRICATED BLADE AND BUCKET ROTOR ASSEMBLY Filed Jan. 12, 1959 2 Sheets-Sheet 1 "JEIH Feb. 14, 1961 R. E. WARREN ETAL 2,971,745

FABRICATED BLADE AND BUCKET ROTOR ASSEMBLY Filed Jan. 12, 1959 2 Sheets-Sheet 2 INVENTORS. P055876 W466i United States Patent FABRICATED BLADE AND BUCKET ROTOR ASSEMBLY Robert Evans Warren and William Widlansky, Marblehead, Mass., assignors to General Electric Company, a corporation of New York Filed Jan. 12, 1959, Ser. No. 786,404

Claims. (Cl. 253-77) This invention relates to axial flow rotor assemblies for use in gas turbine powerplants, and more particularly to an improved tiered rotor blade assembly.

It is well known in the prior art that, in aircraft gas turbine powerplants operated at relatively low flight speeds, thrust can be augmented by providing a compressor or fan for supplying a flow of ambient air to the 'Patented Feb. 14, 1961 larly pointing out and distinctly claiming the subiect matter which we regard as our invention, it is believed that the invention will be better understood from the following description, taken in conjunction with the accompanying drawings in which: v

Fig. l is an exploded view, in perspective, of a portion of a rotor assembly embodying our invention;

; tion of the shroud and blade assembly; and

stream of working fluid exhausted from the turbine.

An exampie of suchan arrangement is shown and described in US. Patent No. 2,455,458 to Frank Whittle. The compressor or fan may conveniently comprise a group of compressor blades concentrically mounted upon'the peripheral surface of a turbine wheel driven by the exhaust stream, together with shroud and duct means confining and separating the exhaust stream and the ambient air stream. The duct means is terminated downstream of the concentric turbine and compressor,

so that the flow of ambient air joins the turbine exhaust 5 stream and increases the mass rate of flow fluid. Y It is an object of this invention to provide an improved rotor assembly of the kind just described, having concentric rows of turbine and compressor blading, that is simple, lightweight and compact, and in which operational stresses are minimized. It is a further object of this invention to provide an improved rotor assembly wherein each turbine or com pressor blade element may be easily removed to permit individual-replacement.

Further objects and advantages of our invention will become apparent a the following description proceeds. .--Briefly stated, and-in accordance with one embodi ment of our invention, we provide a concentrically arranged turbine bucket and compressor blade rotor assembly, fabricated from separate blade elements. A turbine rotor disc is provided with a plurality of circumferentially arranged, bucket root-receiving slots, which receive the turbine bucket roots in a conventional manner. Each bucket is provided at its outer extremity with radially outwardly extending tangs which are received in circumferentially arranged radial slots located in an annular segmented shroud. The shroud is constructed from lightweight arcuate segments, each of which encloses a plurality of turbine buckets, thereby minimizing gas leakage through the shroud between adjacent buckets. Concentrically mounted about the shroud are a plurality of compressor blades having radiallyinwardly-extending tangs positioned to interen gage with the turbine bucket tangs. Alignedholes in the tangs and in the shroud are positioned to receive blade locking means for releasably.securing the blades and the; buckets 'tothe shrouds. The foregoing structure allows a lightweight, compact, two-tiered rotor assembly in which the compressor blades ad turbine buckets not only'lmay be fabricated from different materials, but are alsorreleasably secured to the intermediate shroud for individual replaceability.

of the motive positioned to While the specification concludes with claims particu- Fig. 6 is a side elevation view, partially in section, of the blade, shroud and bucket interlocking structure, taken along the line 66 in Fig. 5.

Referring to Fig. 1, a rotor disc 1, having an integral stub shaft 2, is provided with a plurality of circumferentially arranged axially-extending slots 3 positioned to receive the roots 4 of a plurality of biades, one of which is shown at 5. A plurality of lockingmembers, one of which is shown at 6, are inserted in slots 3 beneath roots 4 to secure the blades to the disc in a conventional man ner, forming no part of this invention.

The rotor assembly includes a plurality ofinner blade elements, one of which is shown at 5, a plurality of corresponding outer blade elements, one of which is shown at 7, a plurality of elongated arcuate segmental shroudmembers, a portion of one of which is shown at 8,-and a plurality of blade retaining pins, one of which is shown at 9. In the preferred'embodiment of our invention, the inner tier of blade elements will hereafter be referred to as turbine buckets, and the outer tier of blade elements will hereafter be referred to as compressor blades; however, it is apparent that with slight modifications the inner tier of blading could be utilized as compressor blades and the outer tier of blading could be utilized as turbine buckets. Referring to our preferred embodiment, as shown in Fig. 1, a turbine bucket 5 having an integral platform 5a, is provided with a plurality of radially outwardly extending tangs 10 having aligned openings 11 therein. The turbine buckets form an inner tier of blading. A substantially continuous, annular, segmented shroud, a portion of which is shown at 8, is provided with a plu rality of sets of inner and outer radial slots, 12 and 13, respectively. The bucket tangs 10 are received in radial slots 12 of the shroud segment 8 and platforms 5a abutan inner sheet metal portion 24 of shroud 8.

An outer tier of compressor blades 7 is detachably mounted radially outward of the inner tier of turbine buckets and the detachably mounted shroud segment 8; Each compressor blade 7 has an integral' platforrn 7a and is provided with a plurality of radially inwardly extending tangs 14 which are received in shroud slots 13 and are positioned to intercalate with the tangs 10 of a corresponding turbine bucket. Platforms 7a abut an outer sheet metalportion-25 of shroud 8. The com pressor blade tan-gs 14-are provided with holes 15 p os i tionedto align with holes 11 in tangs 10 when the blades are assembled in the shroud member. Each .shroud member 8 is also provided with aplurality of holes 16 align with tang holes 11 and 15 in ass mr Figs. 2,4, 5 and 6 'illustrate'more clearlyth'e mapper of assemblyfof'tlieblade, shroud and'bucket. Theta rigs 10 of each turbine bucket 5 are inserted into slots 12 in shroud member 8. The tangs 14 of each corresponding compressor blade 7 are inserted into slots 13 in shroud member 8. The inner radial slots 12 are axially staggered with respect to the outer radial slots 13, so that taiig's' 10 and 14 are intercalated in assembly; The bucket- 5 and the blade 7 are releasably secured to one another and to the shroud 8 by means of a blade retain= ing pin 9 which is passed through aligned openings 11 15 and 16 in the bucket, blade and shroud respectively;

In order to securely hold blade retaining pin 9 in' place after assembly, the pin is provided with an enlarged por-' tion 17 at one end thereof and a longitudinal slot 18" at the other end. Slot 18 includes a recessed portion 19 located intermediate the ends o f the blade retaining pm 9. A locking pin 20, best seen in Fig; 3-, has an upstanding portion 21 at one end thereof and a tab portion 22 at the other end. Referring to Fig. 6, pin 20 is positioned in slot 18 with portion 21 engaged in recess 19. Upon assembly, the enlarged portion 17 of the blade retaining pin 9 engages with one of the tangs 10 or 14, and the tab portion 22 of the locking pin 20 is bent down as shown to engage with one of the tangs 10 'or 14 at the other end of the intercalated stack of tangs, thereby locking the blade retaining pin 9 in place and securing the assembly.

As is most clearly shown in Fig. 5, each shroud mem her 8 is preferably fabricated from a cellular type honey-- comb material 23. The cellular material is securely fastened, as by brazing, to inner and outer sheet metal portions 24 and 25, thus forming a lightweight, rigid shroud member. Referring to Fig. 4, the inner sheet 24 of shroud 8 is provided with substantially axial projections 26 on the upstream and downstream shroud edges. Seals 27, shown in phantom view in Fig.- 4, are mounted on a stationary annular duct structure which separates the" turbine and compressor flow paths.- The projections have radial flanges 28 which cooperate with seals 27 to provide an effective seal preventing the flow of hot motive fluid, from the flow path around the buckets, past the shroud and into the flow path around the compressor blades.

.It will be apparent that We have provided a tiered bucket and blade rotor assembly in which the inner turbine buckets may be made of a high density material having good high temperature strength characteristics, while at the same time the outer tier of compressor blades may be made from a low density material having good low temperatu'r'e strength characteristics. The use of lightweight outer blades will efiectively reduce steady state centrifugal stresses present in the turbine buckets. Inasmuch as each blade and bucket are releasably secured to one another and to the shroud, they may be individually replaced in the event of damage. The shroud 8, in addition to providing a releasable securing means for the blades 7 and buckets 5, mso serves to minimize vibratory stresses set up in the blades and buckets by providing circumferential restraint and a consequent damping e'fiect. Further, the shroud, because of its substantially continuous annular construction, minimizes the leakage of hot gases through the shroud.

While we have shown and described a particular em bodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention What w claim as new and desire to secure by' Letters Fatent of the United States is:

'1'. In combinationwith a rotor for use in a gas turbine powerplant, a circumferential row of inner blade elements secured to said rotor and having radially outwardly extending first s aced-a art tan s formed therein, a plurality of outer blade elements arran ed concentrically about said row of inner blade elements each or said outer blade elements having radially inwardly extendin round 4 spaced=apart tangs formed therein and positioned to interengage with said first tangs a corresponding one of said inner blade elements, an annular segmented shroud member arranged concentrically between said rows of blade elements and having a plurality of radially disposed slots positioned to receive said first and said second tangs, interengaging tangs of corresponding ones of said inner and outer blade elements and said shroud member having aligned openings therein, and blade locking means received in said aligned openings for releasably' securing corresponding ones of said inner and outer blade elements to said shroud member.

2. In combination with a rotatably mounted axial flow rotor for use in a gas turbine powerplant, a first row of radially inner blade elements secured about the periphery of said rotor, an annular segmented shroud arranged concentrically about said first row and having a plurality of radial slots formed therein, a second row of radially outer blade elements arranged concentrically about said first row and said shroud, each of said outer blade elements radially aligned with and corresponding to one of said inner blade elements, each of said inner blade ele ments having spaced-apart tangs extending radially out- Wardly into said radial slots, each of said outer blade elements having spaced-apart tangs extending radially inwardly into said radial slots and intercalated with said outwardly extending tangs of a corresponding inner blade element, said shroud and said tangs of corresponding blade elements having aligned openings therein, and a plurality of blade locking means received in said aligned openings of said corresponding blade elements and said shroud member for releasably securing said inner and outer blade elements to said segmented shroud.

3. Ali axial flow rotor assembly as defined in claim 2, wherein each of said blade locking means comprises a blade retaining pin having an enlarged portion at one end thereof for engaging one of said tangs of said cor responding blade elements, said retaining pin being formed with a longitudinal slot extending from the oppos'ite end thereof and terminating in a recess intermediate the ends of said retaining pin, and a blade locking pin positioned within said slot, said blade locking pin having an upstanding portion at one end thereof engaging said recess and a portion at the other end thereof adapted to be bent into engagement with another of said tangs of said corresponding blade elements, whereby said blade retaining pin is locked in place within said aligned openings.-

4. An axial flow rotor assembly for use in a gas turbine powerplant, comprising a rotor disc having a plurality of bucket root-receiving slots located about the periphery thereof, a circumferential row of turbine buckets having root port-ions secured in said slots, each of said buckets having radially outwardly extending spaced-apart tangs, a segmented annular shroud member concentrically located about said buckets, a circumferential row of compressor blades arranged concentrically about said row of buckets and said shroud member, each of said blades radially aligned with and corresponding to one of said buckets, said blades having radially inwardly extending spaced-apart tangs, said shroud member formed with a plurality of radial openings receiving said tangs of corresponding one of said buckets and blades in intercalated relationship, said shroud member and said tangs of corresponding ones of said buckets and blades having aligned openings therein, and locking means received in said aligned openings for releasably securing said buckets and blades to said shroud.

5. In' combination with a rotatably mounted axial flow rotor for use in a gas turbine powerplant, a first row' of radially inner blade elements secured about the periphery of said rotor, an annular segmented shroud arranged concentrically about said first row, said shroud formed with first radial slots in a radially inner surface thereof with second radial slots in a radially outer surface thereof, a second row of radially outer blade elements arranged concentrically about said first row and said shroud, each of said outer blade elements radially aligned with and corresponding to one of said inner blade elements, each of said inner blade elements having spacedapart tangs extending radially outwardly into said first slots, each of said outer blade elements having spacedapart tangs extending radially inwardly into said second slots, said inner and outer slots being spaced in axially staggered relationship such that upon assembly said tangs of corresponding inner and outerblade elements are intercalated, said shroud and said tangs of corresponding blade elements having aligned openings therein, and a plurality of blade locking means received in said aligned openings for releasably securing said inner and outer blade elements to said segmented shroud.

References Cited in the file of this patent UNITED STATES PATENTS 1,998,951 Downer Apr. 23, 1935 2,398,140 Heppner Apr. 9, 1946 2,518,660 Browne Aug. 15, 1950 2,625,366 Williams Jan. 13, 1953 2,801,789 Moss Aug. 6, 1957 FOREIGN PATENTS 585,331 Great Britain Feb. 5, 1947 

